It is known that a rich flora of primarily lactic acid-producing bacteria occur in the urogenital region of healthy women, both before and after the menopause. These bacteria have antagonistic properties against different occurring uropathogens, which is thought to be due to their ability to produce different antimetabolites. A particularly important antimetabolite is, of course, lactic acid which has an inhibiting effect on different pathogenic microorganisms by lowering the pH in the urogenital environment.
It is also known that the production of lactic acid is disturbed in conjunction with menstruation, resulting in a decrease in the amount of lactic acid produced. This will, of course, result in a higher pH-value, which favours those microorganisms that generate bad-smelling substances, among other things. The growth of microorganisms is also liable to cause irritation of the skin and the mucous membrane in the urogenital region.
Those methods afforded by known techniques in counteracting these problems to a large extent involve the use of different tampons and sanitary napkins which have been impregnated with different substances that lower the pH-value in the present context. For instance, SE 9100364-0 and SE 8505491-4 describe tampons and napkins which have been impregnated with cultures of living lactic acid bacteria. Even though this type of technical solution would seem to be sympathetic at first sight, since there are used lactic acid bacteria which occur naturally in the urogenital region, a closer study of these specifications reveals that the technique applied is both very complicated and highly sensitive. For instance, it is necessary to isolate the bacteria cultures and to determine their type before they can be finally incorporated in the tampon or the napkin with the aid of some form of adhesive. A further drawback with this technique, as pointed out in EP-Al 0,130,356, is that the pH-value in the vagina in conjuction with menstruation already lies in the alkaline region when the tampon or the napkin is applied. This inhibits the growth of the lactic acid bacteria and therewith reduce their lactic acid production, or at least cause this production to fluctuate greatly.
The last-mentioned document, EP-Al 0,130,356, describes in turn a tampon whose absorbent body is impregnated with a citrate-containing buffer solution. Naturally, a buffer solution of this nature must be considered foreign to the body at least in the present context, although the most serious drawback with this technical solution resides, also in this case, in the additional and complicated working steps occasioned by the actual impregnation process in tampon manufacture.
Other technical solutions are described in U.S. Pat. No. 3,794,034 and DE-Al 2,309,575. These solutions, however, are also encumbered with the same drawbacks.
A somewhat different technical solution is described in GB-A-2,107,192, which relates to a tampon which may have a polylactic acid for instance incorporated in its absorbent body. It is proposed that this polymer is admixed in the fibre pulp of the absorbent body, in a powder, granule or fibre form. This technical solution thus also necessitates the application of at least one additional stage in the manufacture of the tampon, namely the stage in which the polylactic acid is mixed in the fibre pulp. The object of the tampon is to lower the pH-value within the tampon, whereas, on the other hand, the pH-value externally of the tampon is permitted to adopt such high values as 4.5.
WO 91/08726 also describes the use of polylactic acid in absorbent articles, more specifically in the top and bottom sheets of such articles. These sheets, however, are designed solely to fulfil a specific purpose, namely that the absorbent article shall be considered to represent an article which is biologically degradable after use. The document makes no mention of the possibility that the polylactic acid could be used to adjust the pH-value with the purpose of counteracting bad smells or irritation of the skin/mucous membrane.
JP 61-149 160 also describes the use of polylactic acid in absorbent articles for medical purposes. In this case, the polylactic acid is present in the form of a sponge. The only reason given for the use of precisely polylactic acid is to render the sponge biologically degradable.
WO 90/01521 describes plastic films comprised of polylactic acid, among other things. However, these plastic films are intended solely for conventional packaging purposes. The document gives no indication that the film could be used in absorbent articles.
There is an obvious need for biologically degradable tampons and sanitary napkins with which bad smells and the risk of irritation of the skin and mucous membrane in the urogenital region of the user can be counteracted and controlled continuously when the article is in use, and which can also be produced in a simple fashion.